Typically, an agricultural harvesting machine such as a combine gathers crop from a field and transports the crop by means of a feeder house to a threshing and separating device located inside the combine. Generally, threshing refers to removing grain, beans, seeds or kernels, hereinafter referred to as just grain, which are desired to be collected, from husks, cobs, pods, stems, hulls and other portions of the plants being harvested, which are to be discarded. The threshing and separating device delivers the crop to the cleaning system of the combine, which includes a plurality of sieves. An upper sieve allows clean grain and some crop material such as pod, husk and cob fragments and hulls still containing grain to fall through it, and a lower sieve is adjusted so that only clean grain is allowed to pass through it. The clean grain and crop material including some grain that falls through the upper sieve, but does not pass through the lower sieve, is called tailings. In some harvests, the tailings can include a significant amount of grain (e.g. beans, seeds or kernels) fully or partially contained, held or retained in partial or full pods, husks, cobs and hulls. For example, when harvesting soybeans, some areas of a field or an entire field may include plants which matured later for a variety of reasons and thus have somewhat green bean pods, which, as a result of their less than full maturity, are not fully opened by the initial threshing operation. As a result, in many cases it is desired or required for this material to be threshed and/or cleaned again.
Prior methods and apparatus for returning the tailings to the threshing and cleaning systems conveyed them to one side of the combine with a rotary helical auger located in a housing or trough. The internal surfaces of the known housings and troughs are smooth, and become polished with use, due to abrasive properties of the tailings and dust which is typically mixed with the tailings. As a result, the tailings move smoothly along the internal surfaces with virtually no actions that would tend to loosen or release grain held in pods, husks, hulls and the like. The tailings are then carried by a conveyor, typically a paddle and chain conveyor, back to the combine threshing mechanism. Some combines have used a rethreshing device which is separate from the threshing system which helps save capacity on the threshing system by rethreshing the tailings separately from new crop coming into the combine. The auger feeds material into the rethreshing device and then the material is conveyed back to the cleaning system. Both single impeller/blowers and augers have been used to convey this material back to the cleaning system. These rethreshing devices are usually convertible, enabling the operator to manipulate the machine to be more or less aggressive, depending on such factors as the amount of unreleased grain contained in the tailings, and vulnerability of the grain to damage during processing.
What is sought is an element for a tailings conveyor which reduces the requirement or need for aggressive rethreshing of tailings and thus the risk of damage to grain resulting therefrom, and which improves the throughput capability and efficiency of a rethreshing system.